Whenever cataracts or other conditions require, the natural lens of the human eye can be removed and replaced with an intraocular lens (IOL). An intraocular lens comprises an optic or lens and one or more fixation members which are ordinarily formed of resilient filaments for fixing the optic in the proper position within the eye so that it can direct light toward the retina.
In one common form of intraocular lens, the optic is constructed of a rigid, non-deformable material such as polymethylmethacrylate (PMMA). In a second type of intraocular lens, the optic is constructed of a deformable material, such as silicone or hydrogel. A deformable optic can be rolled or folded for insertion through an ocular incision, which is smaller than the undeformed diameter of the optic. An important advantage of an intraocular lens having a deformable optic is that, when it is rolled or folded, it can be inserted through a smaller ocular incision than can a rigid IOL. This small incision reduces the trauma to the patient, heals faster than a larger incision needed for most rigid IOLs and provides other advantages.
One problem with an intraocular lens having a deformable optic is in the attachment of the fixation member or members to the optic. One way to accomplish this is to utilize separate fixation members and attach them to the optic. These separate fixation members, which are commonly constructed of PMMA or polypropylene, are typically fine hair-like strands. It is somewhat difficult to attach these fine hair-like strands to a deformable optic in a way that will assure that the strands will not pull out from the deformable optic. One way to address this problem is to shape the inner end portions of the strands so that it is difficult to pull them out of the optic. Examples of this are shown in Knight et al U.S. Pat. No. 4,834,751 and Christ et al U.S. Pat. No. 4,790,846.
Another approach is to employ fixation members which are constructed integrally with the optic (i.e. of the same material as the optic so as to form a one piece IOL). However, because of the soft, deformable nature of the foldable optic material, the integral fixation members would need to be large and relatively thick in order that they would have sufficient size to adequately retain and position the optic within the eye. However, thickening of the integral fixation members would give the rolled or folded intraocular lens a larger cross-sectional area than would exist without such thickening of the fixation members, and this, in turn, would require a larger incision than would otherwise be required for the optic alone.